This invention relates to a scroll type refrigerant compressor, and more particularly, to a sealing structure for insulating the suction chamber and the discharge chamber of the compressor casing.
Scroll type refrigerant compressors are well known in the prior art. For example, Japanese Patent Application Publication No. 56-156492 discloses such a compressor which includes two scrolls, each having a circular end plate and an involute spiral element. The scrolls are maintained angularly and radially offset from each other so that the spiral elements interfit to form a plurality of line contacts between their spiral curved surfaces to thereby seal off and define at least one pair of fluid pockets. The relative orbital motion of the two scrolls shifts the line contacts along the spiral curved surfaces and, as a result, the volume of the fluid pockets decreases with compression.
Referring to FIG. 1, a scroll type refrigerant compressor 1 in accordance with the prior art is shown. Compressor 1 includes a compressor housing 10 having a front end plate 11 and a cup shaped casing 12, which is attached to the rearwardly facing surface of front end plate 11 to define an inner chamber between the inner wall of casing 12 and the surface of front end plate 11. Disposed within the inner chamber of cup shaped casing 12 are a fixed scroll 13 having a circular end plate 131 from which a spiral element 132 extends, an orbiting scroll 14 having a circular end plate 141 from which a spiral element 142 extends, a driving mechanism 15 and a rotation preventing/thrust bearing device 16. A drive shaft 151 penetrates an opening 111 in front end plate 11 and is rotatably supported by front end plate 11 through a bearing 17. Driving mechanism 15 is operatively coupled to drive shaft 151, and is connected to orbiting scroll 14 to effect orbital movement of the orbiting scroll during rotation of the drive shaft. Rotation of orbiting scroll 14 is prevented by rotation preventing/thrust bearing device 16. Scrolls 13 and 14 are maintained regularly and radially offset from each other so that spiral elements 132, 142 interfit to form a plurality of line contacts between their spiral curved surfaces which seal-off and define at least one pair of fluid pockets. The orbital movement of orbiting scroll 14 relative to fixed scroll 13 shifts the line contacts along the spiral curved surfaces of spiral elements 132, 142 which changes the volume of the fluid pockets.
Circular end plate 131 of fixed scroll 13 partitions the inner chamber of cup shaped casing 12 into a suction chamber 18 and a discharge chamber 19. A sealing structure 20 (FIG. 2) is formed in the outer peripheral wall of circular end plate 13 to insulate suction chamber 18 and discharge chamber 19. The sealing structure 20 includes a circumferential groove 21 formed in the outer peripheral surface of circular end plate 131 and an O-ring seal element 22 disposed in the circumferential groove 21.
Formation of circumferential groove 21 is accomplished by a cutting process, comprising seven steps, shown in FIGS. 3a through 3g in which circular end plate 131 is mounted for rotation proximate a surface cutting tool. In a first step, shown in FIG. 3a, the outer peripheral surface 131a for circular end plate 131 and the outer circumferential portion 131e of the surface of circular end plate 131 are cut by a surface cutting tool 201 which is attached to a numerical controlled lathe (not shown). In steps 2-4, shown in FIGS. 3b through 3d, respectively, outer peripheral surface 131a of circular end plate 131 is cut by a groove cutting tool 202. Typically, groove cutting tool 202 will have a vertical sectional view similar to that of circumferential groove 21, i.e., the groove cutting tool 202 is used as a forming tool. The final steps in the process are shown in FIGS. 3e through 3g, in which the corners of circumferential groove 21 are rounded by groove cutting tool 202.
There are a number of problems associated with this technique for forming a circumferential groove in the outer peripheral surface of the circular end plate. One problem is that the tip of the groove cutting tool is easily broken, which destroys is utility as a forming tool. It is also difficult to precisely control the dimensions of the groove to within a certain standard because of sticking residual material left at the tip of the groove cutting tool and within the groove itself during the cutting operation. In addition, the process is time-consuming and requires a plurality of cutting tools.